The present invention relates generally to non threaded fasteners that may be used to adjustably attach two materials or items. In particular, the present invention relates to pull pins that lock in a forward position. Pull pins are generally used for applications where items or materials slide proximal to one another and adjustments are made as to their positioning relative to each other. Some applications for pull pins may include telescopic legs having adjustable heights, adjustable tubing, and safety gates having adjustable widths, as an example. A pull pin is generally threaded through a hole in a first surface or material, with the pin shaft portion extending through a hole in the second material. The second material generally has a plurality of spaced apart holes. The pull pin shaft may be pulled by a handle or other pulling mechanism to retract the pin from a first hole in the second material, thereby releasing the material and allowing for adjustment. When in a desired position, the pull pin may be released, by a biasing force in the forward direction, to engage the pin shaft in a second hole to lock the materials in a second position.
Pull pins are well-known in the art, however, present pull pin designs have some deficiencies which limit their usefulness and longevity. For example, in time, the holes on the adjusting material (the second material) may become worn and misshaped. Instead of remaining circular, holding the pin snugly in place, the hole may become elongated. Furthermore, the surfaces surrounding the hole may become beveled. As such, the pull pin shaft can be easily forced in and collapsed, thereby releasing the engagement between the two materials. As such, there remains a need for a pull pin that locks in the forward position so as to prevent the undesirable inward pushing of the pull pin shaft, until a certain action is applied to the pull pin which releases the lock and allows the pin shaft to be retracted.